Most modern memory is based on the evolution of magnetic recording. One form of magnetic memory is a hard disk wherein magnetic bits of information are stored on a magnetic film medium in very small localized regions. Depending on the magnetization within a region, each region represents either a logic high or logic low value (i.e. a “1” or “0”). The regions are electronically read via moving mechanical read/write heads. The heads are mounted proximate a spinning disk supporting a magnetic film. A read head operates by sensing changes in the resistance of the sensor in the read head induced by the data bit regions as they pass under the read head. A write head stores data on the disk by utilizing magnetic flux to set the direction and amplitude of the magnetic moment for each bit region passing beneath the write head.
Disk storage has a limited storage lifetime, bit density, and volatility. The magnetic medium used in traditional disk storage degrades within 10 years. The information is stored in small magnetic bit regions through magnetizing each region in a particular direction. Over time, the magnetization of the bit regions is corrupted by external electromagnetic forces, through prolonged exposure to the Earth's magnetic field, or through thermal upsets. Thermal upsets are statistical processes that occur when the magnetization of a bit region is thermally activated to overcome the anisotropy barrier.
Bit density of conventional hard disks is near 200 Gbits/in2; however, bit region size is limited by the superparamagnetic limit. Traditional magnetic recording is approaching the superparamagnetic limit. Thus, further advances in storage density using traditional storage techniques is becoming increasingly difficult.
As electronic recording evolves and more information is digitized, there exists not just a critical necessity for storage volume but also storage permanency. Therefore, a need exists for high density, stable, non-volatile memory with a longer storage lifetime.